The role of RNA polymerase(s) in the differentiation of the slime mold Physarum polycephalum will be investigated. This organism undergoes two types of differentiation in response to appropriate ssifts in its environment. The first is sporulation, an irreversible process. The second is spherulation, which is reversible. The basic plan of the research project will be to explore changes in the RNA polymerases during sporulation and spherultion in the slime mold. Accordingly, the polymerases will be purified from vegetative, sporulating and spherulating molds and their catalytic and structural properties will be compared. Both the nucleoplasmic and the nucleolar polymerases will be studied. Changes in the following properties will receive special attention: salt and metal ion requirements, template specificity, senitivity to inhibitors, charge (reflecting adenylation or phosphorylation) and subunit structure. Charge differences will be investigated using urea-polyacrylamide gel electrophoresis and subunit structures will be studied with SDS-polyacrylamide gel electrophoresis. Dissociable factors, possibly including sigma-like initiation factors will also be sought in molds in all three differentiated states. Screening for such factors will utilize a non-nicked double-stranded slime mold DNA template from the "transcribed" fraction, and the highly purified slime mold polymerases. The factors, if they are indeed found, will be purified and compared with respect to their charges (urea gels), structures (SDS gels) and their influence on transcriptive specificity. This latter property can be investigated to a limited degree using the technique of RNA-DNA hybridization competition.